1. Field of the Invention
This invention relates to an electroplating apparatus for electroplating a sheet-shaped article, more particularly to an electroplating apparatus, which includes an electrolyte-spraying casing that is provided with a conducting net for distributing evenly anode current.
2. Description of the Related Art
Referring to FIG. 1, a conventional electroplating apparatus 1 for electroplating a sheet-shaped article 10, such as a circuit board, is shown to include a feeding roller unit 11, a first spraying unit consisting of a pair of upper and lower anode nozzle units 13, 14, and an electrolyte-supplying pump unit 15. The article 10 is formed as a cathode, and is conveyed between the anode nozzle units 13, 14 by means of the roller unit 11. The anode nozzle units 13, 14 spray an electrolyte onto top and bottom surfaces of the article 10. When electric current flows through the electrolyte, metal ions in the electrolyte move toward, and are reduced and deposited on the article 10 to form a single layer of metal coating.
Referring to FIG. 2, a series of additional spraying units, each consisting of the anode nozzle units 13, 14, can be provided behind the first spraying unit in order to form several layers of metal coatings on the article 10 in sequence. The aforesaid conventional electroplating apparatus 1 suffers from the following drawbacks:
(1) Uneven distribution of the electrolyte on the article 10: Because the electrolyte is sprayed from the nozzle units 13, 14, it is concentrated on the areas of the article 10, to which the units 13, 14 are directed. In addition, it is difficult for the electrolyte to access the portions of the article 10 that are disposed adjacent to the feeding roller unit 11. Furthermore, the amount of the electrolyte deposited on the top surface of the article 10 is more than that on the bottom surface of the same.
(2) Uneven thickness of the metal coating on the article 10: Because the nozzle units 13, 14 cannot distribute an anode current evenly, it is impossible to obtain a uniform thickness of the metal coating on the article 10.
An object of this invention is to provide an electroplating apparatus with a spraying unit, which includes a pair of upper and lower casings that can maintain an even electrolyte distribution on top and bottom surfaces of a sheet-shaped article.
Another object of this invention is to provide an electroplating apparatus with an anode current-conducting assembly, which includes a conducting net and two conducting units and which maintains an even anode current distribution, thereby forming a uniform thickness of a metal coating on an sheet-shaped article.
According to this invention, an electroplating apparatus includes a plurality of feeding rollers adapted to advance a sheet-shaped article, and a spraying unit. The spraying unit has a pair of upper and lower casings, each of which includes a casing body defining a chamber, and a net plate disposed to confront with the article. An electrolyte is sprayed from the chamber via meshes in the net plate and onto a side surface of the article. An anode current-conducting assembly includes a conducting net that is disposed fixedly within the chamber and that is superimposed on the net plate so as to cover the meshes in the net plate, and two conducting units respectively in electrical contact with two opposite side portions of the conducting net so as to supply electric current to the conducting net.
Because the electrolyte is sprayed evenly from the meshes in the net plate, it can be distributed evenly onto the article. Furthermore, because anode current flows evenly into the electrolyte in the chambers via the conducting net, a metal coating with a uniform thickness can be formed on the article.